Thus, the thermalresistance of the joint is directly proportional to the joint thickness and inversely proportional to the thermal conductivity of the medium making up the joint and to the size of the heat transfer area.

Thermalresistance is minimized by making the joint as thin as possible, increasing joint thermal conductivity by eliminating interstitial air and making certain that both surfaces are in intimate contact.

Thermally conductive compounds are an improvement on thermal grease as these compounds are converted to a cured rubber film after application at the thermal interface.

The thermalresistance of an oscillator package is defined as the temperature difference that occurs between the semiconductor element within the package and the package's surface or ambient atmosphere when the device consumes 1 watt [W] of power.

Thermalresistance is an indication of the heat transfer from the semiconductor device through all of the package materials out to the open environment.

is defined as the thermalresistance from the semiconductor junction to the case of the oscillator (junction-to-case).

In physics, thermal conductivity, λ, is the quantity of heat transmitted, due to unit temperature gradient, in unit time under steady conditions in a direction normal to a surface of unit area, when the heat transfer is dependent only on the temperature gradient thermal conductivity = heat flow rate / (distance &times; temperature...

The R-value is a non-SI measure of thermalresistance used in housing insulation.

The (A tetravalent nonmetallic element; next to oxygen it is the most abundant element in the earth's crust; occurs in clay and feldspar and granite and quartz and sand; used as a semiconductor in transistors) SI units of thermalresistance are:

where is the thermalresistance of the bond between the transistor's case and the metalwork.

We use the general principle that the temperature drop across a given thermalresistance with a given heat flow through it is:

The thermal conductivity of a material is equivalent to the quantity of heat that passes in unit time through unit area of a plate, when its opposite faces are subject to unit temperature gradient (e.g.

Since diamond has such a high thermal conductivity, natural blue diamond much higher still, one may test gems to determine if they are genuine diamonds using a thermal conductance tester, one of the instruments of gemology.

For general scientific use [2]class="external" target="_blank">[1, thermal conductance is the quantity of heat that passes in unit time through a plate of particular area and thickness when its opposite faces differ in temperature by one degree.

In practical circumstances, this resistance cannot be an invariant quantity designated by one number, because the orientation of internal conduction heat flow paths changes in response to changes in the thermal environment.

However, in doing so, the resulting 'thermalresistances' lose their physical meaning completely, as argued in Ref. 4, and one may wonder if the term 'thermalresistance' should be kept, on account of the persistence of the analogy in the minds of most scientists and designers for some time to come.

In all cases, a thermalresistance can be defined, but in many practical cases, the physical significance of the definition is meaningless, with the exception of those definitions which incorporate the ultimate heat sink (an ambient at uniform temperature) as one of the nodes.

Terms such as 'thermalresistance' and 'degrees C / Watt' are a little daunting for the uninitiated, and the purpose of this article is to explain how thermal transfer works, from the transistor die until it is finally dispersed into the atmosphere.

Towards this end, an electrical analogue may be drawn, showing the thermal generator as a current source, thermalresistance as a resistor and the thermal inertia (or transient capacity) of the various materials as a capacitor.

Although the thermalresistances for each of the transistors remain the same, the resultant thermalresistances for a "parallel pair" are effectively halved.

The thermalresistance is obtained by taking the reciprocal of the sum of the kA factors where A is the cross-sectional area for each layer in the thermal path and k is the thermal conductivity of the material.

Because the intrinsic thermalresistance in the CPGA example is so poor, the external resistance of the heat sink to the ambient does not materially change the intrinsic thermalresistance.

Thermalresistance can be reduced by increasing the thermal conductivity of the various materials involved and/or by increasing the cross-sectional area.

www.chipscalereview.com /issues/1198/departmenti1.htm (1042 words)

High thermal resistance bonding material and semiconductor structures using same - Patent 4888634(Site not responding. Last check: 2007-10-18)

A high thermalresistance bonding material for semiconductor chips includes a binder such as epoxy or polyimide and high thermalresistance material dispersed therein such as glass micropheres, glass beads, ceramic microspheres and ceramic beads.

High thermalresistance material such as glass and ceramic beads and microspheres of a generally uniform size are added to the binder.

The glass microspheres increase the thermalresistance of the adhesive, and the uniform distribution of the glass microspheres facilitates uniform thermalresistance between the semiconductor chip 10 and the substrate 12.

In particular, because thermal expansion is at least partially a function of temperature, the relatively greater temperature at the front bearing results in a relatively greater expansion of the front bearing, considered with respect to the expansion of the rear bearing.

A thermal expansion differential between the front and rear bearings, can cause unbalanced, or otherwise improper, rotation and operation of the shaft which is supported by the bearings.

Further, the extended surfaces permit a relative reduction in the thermal gradient along the length of the shaft, thereby contributing to improved heat distribution through the shaft, and reducing the operating temperatures in the front bearing.

Another is to compare the thermalresistance of pentane-blown PIR laminate boards aged in a laboratory environment since early 1998 to those obtained from the mathematical modeling and calculation algorithms developed by Huntsman Polyurethanes.

Another is to compare the thermalresistance of pentane blown PIR laminate boards aged in an uncontrolled ambient laboratory environment since early 1998 to those obtained from the mathematical modeling and calculation algorithms developed by Huntsman Polyurethanes.

ThermalResistance Measurements and Foam Aging The foam thermalresistance was measured according to ASTM C518 with a mean plate temperature of 75oF and temperature difference of 40oF.

An Evaluation of the ThermoChill Radiators(Site not responding. Last check: 2007-10-18)

For low air flow rates, the thermalresistance of the air side is much more important than the fluid side (except for low fluid flow rates).

Increasing the fluid flow rate leads to an improvement for the convection heat transfer, thus a lower thermalresistance, of the fluid side but this is negligible as compared to the air side thermalresistance.

Since the air flow resistance of the HE 120 series is the same per unit area, at the same backpressure the air flow volume of the HE 120.1 would be half of the HE 120.2, while the HE120.3 would be 50% more than the HE 120.2.

thermal-management-testing.com /ThermoChill.htm (2141 words)

2003_February_calccorner(Site not responding. Last check: 2007-10-18)

Using these equations it is possible to estimate heat sinkthermal performance in terms of the thermalresistance from the temperature at the base of the fins to the temperature of the air entering the fin passages.

For purposes of illustration these equations were used to estimate heat sinkthermalresistance for a 50 x 50 mm aluminum heat sink.

Effect of fin height and number of fins on heat sinkthermalresistance at an air velocity of 2.5 m/s (492 fpm).

The soldering method of claim 13 wherein the heating apparatus has an entrance end and an exit end, and wherein the first and second push members are both disposed intermediate the entrance end and exit end of the heating apparatus for allowing the solder paste layers to re-increase their thickness before being allowed to solidify.

The thermalresistance of a soldered joint is known to decrease approximately in proportion with its thickness or with the amount of gas bubbles that are generated by the flux in use with the solder and entrapped in the joint.

Although there was a corresponding increase in thermalresistance, all such increase could be compensated for by the decrease in the total area of the remaining gas bubbles.

Maximum ambient temperature is found to be 105°C. The thermalresistance from case to ambient is 66.3°C/Watt.

ja is a measure of the resistance to heat flow from chip to the surrounding air.

Apply thermal grease to the resistor and pad so the heat flow is directed to the pad.

www.maxim-ic.com /appnotes.cfm/appnote_number/1758 (1107 words)

IngentaConnect Estimating thermal resistance of the bedding assembly from thickn...(Site not responding. Last check: 2007-10-18)

IngentaConnect Estimating thermalresistance of the bedding assembly from thickn...

Thermalresistance was measured using a guarded-hotplate similar to that specified in ISO 11092:1993(E).

While it was possible to predict thickness and thermalresistance of flat bedding from estimated values, extrapolation to bedding during simulated use was considered inappropriate, with significant differences of over 1,000 per cent.

Although based on the same thin-slicing and accelerated-aging concept as ASTM C1303, this method accounts for the effect of permeable facings, or skins, on the long-term thermalresistance of foam insulation in addition to a number of other factors.

Before measuring the thermal performance of a closed-cell foam product, a manufacturer was directed to condition the product for 180 days at 75 F (24 C).

For at least 35 years, the long-term thermalresistance of polyisocyanurate rigid foam insulation has been studied and debated.

After some time the power is turned off and the NTC resistor is used to measure the temperature and more importantly the negative slope of the temperature when the power is off.

A high slope indicates that water is present to cool off the NTC through the thermalresistance of the NTC/steel connection, the steel itself and finally the water.

Thats all fine because a sensor like this may not be as sensitive as the capacitive one because the impedance levels are lower and in case of water that penetrates the enclosure the effect of the volume conductivity will be minimal.